Insulating layers for electrical condensers



Feb. 11, 1930. y sc w n-Z 1,746,366

INSULATING LAYERS FOR ELECTRICAL CONDENSERS Filed Oct. 24, 1 8

INVENTOR ATTORNEY Patented Feb. .11, 1930 LOUIS P. SGHWEITZER, OF NEW YORK, N. Y.

INSULATING LAYERS FOR uncritical. connnnsnas Application filed October 24, 1928. Serial No. 314,637.

My present invention relates generally to electrical condensers, and has particular reference to the insulating layers of so-called paper-dielectric condensers.

In the manufacture of condensers of the foregoing general character, layers of conductlng and non-conducting material, usually foil and paper, are interwound in alternate relationship, the condenser body thus formed is then subjected to heat and vacuum treatment to expel all entrained moisture and air, and it is then impregnated with a suitable dielectric material, such as wax. The length of life of such condensers, and the voltage which they are enabled to withstand,-

are dependent to a large. extent upon the thoroughness of such impregnation. Since breakdown has been found to result from the passage of leakage currents through the 'impregnated insulating layers, it is most important to provide such layers of a character which will most thoroughlywithstand and prevent the passage of such currents.

My invention relates in general to an improvement in the provision of such insulating layers and resides from one aspect in a method of enhancing the thoroughness with which such layers are treated to render them impervious to the passage of leakage currents. From another aspect, my invention resides in the provision of an improved insulating layer to be used in the manufacture of such condensers.

One feature of my invention resides in em-.

denser manufacture, as outlined above, and

seeking to avoid any alteration of such steps,

I have provided a pa er insulating layer which has been treated in a particular manner with an auxiliary dielectric material but which is still susceptible to impregnation inthe usual manner by the usual wax dielectric material. In accordance with my invention,

I start with a porous strip of paper and coat the same on one surface only with an extremely thin and intimately associated continuous layer of unporous dlelectric material.

I have found pyroxylin to be peculiarly adapted to the contemplated purposes.

, Since pyroxylin is an excellent insulating medium, I have found that by providing an extremely fine yet continuous and impervious coating thereof upon one surface of a porous paper strip, such strip is enhanced for insulating purposes by virtue of an initially provided im revious insulating wall. 7 At the same time, t e paper is susceptible to impregnation in the usual manner during the regular course of condenser manufacture.

I have found that the carrying out of my invention results in more than the provision of two superposed and separable layers of paper and pyroxylin. Since the latter is peculiarly capable of application in liquid form, although it dries with great rapidity, it has certain impregnating characteristics which cause the coating to form portions which extend into the interior of the paper through certain pores of the latter and toward the uncoated surface thereof. In this way, an extremely intimate association results, producing a treated paper of a novel character and having qualities of particular value for employment as an insulating layer.

For the attainment of the foregoing objects and such other objects as may hereinafter appear or be pointed out, my invention may be carried out as illustrated in the accompanying drawings, in which- Figure 1 is a cross-sectional View on an enlarged scale of an untreated paper strip;

Figure-2 is a diagrammatic representation of the treatment to which such strip is subjected Figure 3 is a cross-sectional view similar to Figure 1 showing the eifect of such treatment;

Figure 3A is a perspective view of a completely wound and compressed condenser body of the character in which the present insulating layer is employed; and

Figure 4 is a fragmentary cross-sectional view through a completed electrical condenser embodying the improved insulating" such bath comprises liquid pyroxylin, I am enabled to provide an extremely thin yet continuous and impervious coating of the pyroxylin upon the strip 10 in a comparative y simple and inexpensive manner. Since the pyroxylin dries very quickly, I may allow the same to dry merely during its passage from the bath to the roll 12, or I may provide suitable heating means or the like for facilitating such drying.

In Figure 3 I have shown the resultant improved andtreated paper strip. A continuous and unporous coating 15 of pyroxylin presents an exceptionally smooth and unbroken surface 16 on one side of the strip. The other side 17 of the strip still presents the same porous surface as it did before. The coating 15 will be found to have portions 18 extending into the interior of the paper through certain pores of the latter and toward the uncoated surface 17. Thus, it will be seen that my treatment, though resembling impregnation to a certain extent and resembling pure coating to a certain extent is, as a matter of fact, a combination of the two, the, resultant strip being a unitary article having the novel and nnproyed characteristics hereinbefore referred to.

This improvedunitary strip may be supplied in rolls in the-usual manner to the Y ,manufacturers of condensers. It may then be interwound in the usual manner with strips of conducting material such as foil, and the condenser bo ies may be subjected to the heat and vacuum treatment and the customary impregnation.

' A condenser body of the foregoing character is shown in Figure 3A. One end portion 20 comprises superposed edges of one foil strip (for example, the upper strip 19 of Figure 4), and the opposite end portion 21 comprises superposed edges of the other foil strip (for example, the lower strip 19' of Fig- .ure 4). These end portions are completely insulated from each other by the interwound insulating layer ,or layers and are therefore usable as terminals in the completed condenser. Usually, a pair of contact terminals or strips 22 and 23 are made to project outwardly from the end portions 20 and 21. In Figure 3A, I have also shown a sticker or label 24 applied to the free ends of the insulating layers or strips to hold the condenser body in wound condition.

A fragmentary cross-section on a greatly enlarged scale through a portion of the completed condenser is shown in Figure 4. The layers 19 are foil sandwichingmy improved insulating layer between them, the surface 16 being in close contact with one of the foil strips, and the surface 17 bein in close contact with the other foil strip. he usual impregnating medium will have found its way into the paper in the usual manner. and W111 be supplemented by the impervious and noncon-ducting wall .15. As a result, the completed condenser will have improved qualities imparting increased life and improved capability of withstanding high voltages. Leakage currents may find their way through certain portions of the wax but will find it compartaively difficult to pass completely through the insulating layer by virtue of the obstruction presented by the wall 15.

It will be obvious that changes in the details herein described and illustrated for the purpose vention may be made by those skilled 1n the art without departing from the spirit and scope of the inventon as expresse in the appended claims. It is therefore intended that these details be interpreted as illustrative, and not in a limiting sense.

Having thus described my inventlon and illustrated its use, what I claim as new and desire to secure by Letters Patent is- 1. In a wound condenser body comprlsmg alternate layers of conducting and non-conducting material, an insulating layer comprising a strip of'paper susceptlble to 1mpregnation by a dielectrlc liquid medium and a continuous and impervious coating of pyroxylin intimately associated with only one surface of said strip.

2. In a wound condenser body comprising alternate layers of conducting and non-conducting material, an insulating layer comprising a strip of paper susceptible to impregnation by a dielectric liquid medium, and a continuous and impervious coating of pyroxyline intimately associated with only one surface of said strip, said coating of pyroxylin having portions which extend into the interior of the aper through certain pores of the latter and toward the opposite uncoated surface. y

3. In an electrical condenser comprising interwound alternate layersof conducting and of explaining the nature of my innon-conducting material, an insulating la er comprising a strip of porous paper an a continuous unporous coating of dielectric material intimately associated with one surface thereof, and a second dielectric material in intimate impregnatory association with the entire insulating layer.

4. In an electrical condenser comprising interwound alternate layers of conducting and 1G non-conducting material, an insulating layer comprising a strip of porous paper and a continuous coating of pyroxylin intimately associated with one surface thereof, and a second dielectric material in intimate impregnatory association with the entire insulating layer.

5. In an electrical condenser comprising interwound alternate layers of conduotin and non-conducting material, an insulatin ayer comprising a strip of porous paper an a continuous coating of pyroxylin intimately associated with one surface thereof, and a Wax dielectric material in intimate impregnatory association with the entire insulating layer.

6. In an electrical condenser comprising interwound alternate layers of conducting and non-conducting material, an insulating layer comprising a strip of porous paper and a continuous unporous coating of dielectric 3o material intimately associated With one surface thereof and having portions which exr tend through certain pores of the paper toward the uncoated surface of the latter, and a second dielectric material in intimate impregnatory association with the entire insulating layer and filling in the remaining pores.

7. In an electrical condenser comprising interwound alternate layers of conductin and non-conducting material, an insulatingayer comprising a strip of porous paper and a continuous coating of pyroxylin intimately associated with one surface thereof and having portions which extend through certain pores of the paper toward the uncoated surface of the latter, and a Wax dielectric impregnating material extending from said uncoated surface into the interior of the paper and filling in the remaining pores.

- In witness whereof I have signed and sealed this specification this 16th day of October, 1928. 0

- LOUIS P. SCHWEITZER. 

